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Recent Advances in Perturbative QCD and Hadronic Physics July 20-25, 2009

Transverse Spin and Transverse Momentum Effects at COMPASS. Franco Bradamante Trieste University and INFN. Recent Advances in Perturbative QCD and Hadronic Physics July 20-25, 2009. OUTLOOK. the COMPASS experiment results on

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Recent Advances in Perturbative QCD and Hadronic Physics July 20-25, 2009

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  1. Transverse Spin and Transverse Momentum Effects at COMPASS Franco Bradamante Trieste University and INFN Recent Advances in Perturbative QCD and Hadronic Physics July 20-25, 2009

  2. OUTLOOK • the COMPASS experiment • results on • transversity : Collins asymmetries 2 hadron asymmetriesL polarization • Sivers asymmetries • other TMD asymmetries • unpolarised azimuthal asymmetries • exclusive r asymmetries • future plans for SIDIS F. Bradamante

  3. OUTLOOK • the COMPASS experiment • results on • transversity : Collins asymmetries 2 hadron asymmetriesL polarization • Sivers asymmetries • other TMD asymmetries • unpolarised azimuthal asymmetries • exclusive r asymmetries • future plans for SIDIS ECT*, July 23, 2009 F. Bradamante

  4. COMPASS fixed target experiment at the CERN SPS broad physics programme data taking since 2002: muon beam: 160 GeV/c longitudinal polarisation -80% intensity 2·108 µ+/spill (4.8s/16.2s) F. Bradamante

  5. COMPASS • two stages spectrometer • Large Angle Spectrometer (SM1) • Small Angle Spectrometer (SM2) variety of tracking detectors to cope with different particle flux from θ = 0 to θ ≈ 200 mrad SciFi Silicon Micromegas GEMs Straws SDC MWPC W45 MuonWall SM2 E/HCAL E/HCAL SM1 ~ 50 m MuonWall Polarised Target calorimetry, PID RICH RICH detector mbeam • high energy beam • large angular acceptance • broad kinematical range F. Bradamante

  6. COMPASS radiator C4F10 threshold: p~2 GeV/c K ~ 10 GeV/c Polarised Target RICH RICH detector mbeam F. Bradamante

  7. COMPASS Polarised Target mbeam F. Bradamante

  8. The Target System solid state target operated in frozen spin mode during data taking with transverse polarization,polarization reversal after ~ 4-5 days 2002-2004: 6LiD (polarised deuteron) dilution factorf = 0.38 polarizationPT = 50% two 60 cm long cells with opposite polarization • 2006: • PTM replaced with the large acceptance COMPASS magnet (180 mrad) • 2 target cells  3 target cells 2007:NH3 (polarised protons) dilution factorf = 0.14 polarizationPT = 90% F. Bradamante

  9. SIDIS event selection and kinematics • DIS event selection: • Q2>1 (GeV/c)2 • 0.1<y<0.9 • W>5 GeV/c2 F. Bradamante

  10. DIS event selection: Q2>1 (GeV/c)2 0.1<y<0.9 W>5 GeV/c2 SIDIS event selection and kinematics • Hadron selection • pT>0.1 GeV/c • z>0.2 F. Bradamante

  11. OUTLOOK • the COMPASS experiment • results on • transversity : Collins asymmetries2 hadron asymmetriesL polarization • Sivers asymmetries • other TMD asymmetries • unpolarised azimuthal asymmetries • exclusive r asymmetries • future plans for SIDIS ECT*, July 23, 2009 F. Bradamante

  12. Transversity Distribution Function can be measured in SIDIS on a transversely polarised target via “quark polarimetry” all explored in COMPASS F. Bradamante is chiral-odd: observable effects are given only by the product of Tq (x) and an other chiral-odd function

  13. Collins Asymmetry C ± refer to the opposite orientation of the transverse spin of the nucleon PT is the target polarisation; DNNis the transverse spin transfer coefficient initial  struck quark “Collins angle” • C = h-s’ =h+S - p h,s’,Sazimuthal angles of hadron momentum, of the spin of the fragmenting quark and of the nucleon in the GNS from the azimuthal distribution of the hadrons one measures the “Collins Asymmetry” the convolution of TRANSVERSITY and COLLINS FF F. Bradamante Collins effect  azimuthal distribution of the hadrons produced in

  14. Collins Asymmetry - Deuteron data final results from 2002-2004 data asymmetries compatible with zero within the statistical errors (syst. errors much smaller) F. Bradamante

  15. Collins Asymmetry - Fits to Data new results using HERMES (p) and COMPASS (d) piondata, and BELLE data M. Anselmino et al.,Ringberg Workshop on New Trends in HERA Physics 2008Nucl.Phys.Proc.Suppl.191 (2009) 98 F. Bradamante

  16. 2007 run: transversely polarized NH3 target Collins Asymmetry - Proton Data F. Bradamante first results: Transversity 2008 in Ferrara new release: DIS 2009 in Madrid ~2 times more statistics data taking equally shared between transverse and longitudinal

  17. DIS2009 Collins Asymmetry - Proton Data F. Bradamante

  18. Collins Asymmetry - Proton Data comparison with predictions F. Bradamante

  19. OUTLOOK • the COMPASS experiment • results on • transversity : Collins asymmetries 2 hadron asymmetriesL polarization • Sivers asymmetries • other TMD asymmetries • unpolarised azimuthal asymmetries • exclusive r asymmetries • future plans for SIDIS ECT*, July 23, 2009 F. Bradamante

  20. Interference Fragmentation Function Two Hadron Asymmetries azimuthal asymmetry in fRS=fR┴- fs’ fR┴ is the azimuthal angle of the plane defined by the two hadrons A. Bacchetta, M. Radici, hep-ph/0407345 X. Artru, hep-ph/0207309 F. Bradamante

  21. Two Hadron Asymmetries – Deuteron data xF > 0.1 z1,2 > 0.1 Z = z1+ z2< 0.9 RT > 0.05 GeV/c F. Bradamante

  22. K0  DIS2009 Two Hadron Asymmetries – Proton data xF > 0.1 z1,2 > 0.1 Z = z1+ z2< 0.9 RT > 0.07 GeV/c in the valence region signal larger than measured by HERMES F. Bradamante

  23. Two Hadron Asymmetries – Proton data comparison with predictions courtesy of A.Bacchetta still waiting for the BELLE measurement of the IFF F. Bradamante

  24. OUTLOOK • the COMPASS experiment • results on • transversity : Collins asymmetries2 hadron asymmetriesL polarization • Sivers asymmetries • other TMD asymmetries • unpolarised azimuthal asymmetries • exclusive r asymmetries • future plans for SIDIS ECT*, July 23, 2009 F. Bradamante

  25. L asymmetries Information on ∆Tq can be accessed in • 2007 proton data • pT > 23 MeV/c to exclude e+e− pairs • Proton and pion momenta > 1 GeV/c • Q2 > 1 (GeV/c)2 • 0.1 < y < 0.9 • Use of RICH (2007 data) • Λ decay distance DΛ > 7 σD • Collinearity < 10 mrad F. Bradamante

  26. L asymmetries deuteron proton systematic errors smaller than statistical errors from false polarization no dependence on x F. Bradamante

  27. OUTLOOK • the COMPASS experiment • results on • transversity : Collins asymmetries 2 hadron asymmetriesL polarization • Sivers asymmetries • other TMD asymmetries • unpolarised azimuthal asymmetries • exclusive r asymmetries • future plans for SIDIS ECT*, July 23, 2009 F. Bradamante

  28. Sivers Asymmetry hazimuthal angle of hadron momentum Sazimuthal angle of the spin of the nucleon the “Sivers angle” Sand the “Collins angle” C are independent  the Collins and Sivers asymmetries can be disentangled and extracted from the same data in SIDIS on a transversely polarised target the “Sivers DF” the most famous of the TMD parton DF • the Sivers asymmetry • has been measured by the HERMES experiment on proton • different from zero for positive charge particles • compatible with zero for negative charge particles F. Bradamante appears in SIDIS as a modulation in the “Sivers angle”S = h- S

  29. Sivers Asymmetry - Deuteron data final results from 2002-2004 data cancellation between u and d quark contributions in the dueteron F. Bradamante

  30. Sivers asymmetry – proton data statistical errors; systematic errors ~ 0.5 sstat intriguing result ! F. Bradamante

  31. Sivers asymmetry – proton data • from S. Arnold, A. Efremov et al. arXiv:0805.2137 comparison with recent predictions • from M. Anselmino et al. arXiv:0807.0166 F. Bradamante

  32. OUTLOOK • the COMPASS experiment • results on • transversity : Collins asymmetries 2 hadron asymmetriesL polarization • Sivers asymmetries • other TMD asymmetries • unpolarised azimuthal asymmetries • exclusive r asymmetries • future plans for SIDIS ECT*, July 23, 2009 F. Bradamante

  33. SIDIS cross-section Sivers Collins 18 structure functions A Bacchetta, M Diehl, K Goeke, A Metz, P Mulders, M Schlegel (06) 8 modulations (4 LO) allmeasured by COMPASS on deuteron F. Bradamante

  34. “pretzelosity”  Collins FF Other SSAs - Deuteron data two twist-2 asymmetries can be interpreted in QCD parton model and will allow to extract unexplored DFs on deuteron asymmetries compatible with zero : again cancellation between proton and neutron? F. Bradamante

  35. OUTLOOK • the COMPASS experiment • results on • transversity : Collins asymmetries 2 hadron asymmetriesL polarization • Sivers asymmetries • other TMD asymmetries • unpolarised azimuthal asymmetries • exclusive r asymmetries • future plans for SIDIS ECT*, July 23, 2009 F. Bradamante

  36. SIDIS cross-section Sivers Collins 18 structure functions A Bacchetta, M Diehl, K Goeke, A Metz, P Mulders, M Schlegel (06) 8 modulations (4 LO) F. Bradamante

  37. Unpolarised Target SIDIS Cross-Section Cahn effect +Boer-Mulders DF Boer- Mulders x Collins FF+ Cahn effect F. Bradamante

  38. Transversity 2008 Unpolarised Azimuthal Asymmetries summary positive hadrons negative hadrons error bars: statistical errors only F. Bradamante

  39. Unpolarised Azimuthal Asymmetries cos2modulation comparison with theory F. Bradamante

  40. OUTLOOK • the COMPASS experiment • results on • transversity : Collins asymmetries 2 hadron asymmetriesL polarization • Sivers asymmetries • other TMD asymmetries • unpolarised azimuthal asymmetries • exclusive r asymmetries • future plans for SIDIS ECT*, July 23, 2009 F. Bradamante

  41. exclusive r0 asymmetries proton data analysis • selection of exclusive r0 production F. Bradamante

  42. exclusive r0 asymmetries proton data analysis • selection of incoherent r0 production • selection of exclusive r0 production F. Bradamante

  43. exclusive r0 asymmetries proton data analysis • selection of incoherent r0 production • selection of exclusive r0 production • measured asymmetry F. Bradamante

  44. DIS2009 exclusive r0 asymmetries – proton data F. Bradamante

  45. exclusive r0 asymmetries – deuteron data F. Bradamante

  46. OUTLOOK • the COMPASS experiment • results on • transversity : Collins asymmetries 2 hadron asymmetriesL polarization • Sivers asymmetries • other TMD asymmetries • unpolarised azimuthal asymmetries • exclusive r asymmetries • future plans for SIDIS ECT*, July 23, 2009 F. Bradamante

  47. International Effort SIDIS: HERMES at DESY COMPASS at CERN spin experiments at JLab hard pp scattering: spin experiments at RHIC / BNL and several future projects: COMPASS at CERNexperiments at JParc / KEK Panda and PAX at FAIR / GSI Nica at JINR SPASCHARM at IHEP eRHIC, ELIC ENC at FAIR ECT*, July 23, 2009 F. Bradamante

  48. future COMPASS measurements motivations • SIDIS at high energy provides unique information on the transverse spin and intrinsic momentum structure of the nucleon • high energy and high Q2, a guarantee for the hard scale “easy” flavour separation • simple interpretation • access to all the TMD structure functions broad x range • complementary to hard hadron-hadron scattering • the high energy muon beam and the COMPASS spectrometer are unique facilities • CERN is the only place where in the next few years SIDIS measurements can be made at high energy • in the short term, new COMPASS measurements are needed • to perform more precise measurements of the Collins asymmetry • to clarify the compatibility of the HERMES and COMPASS measurements of the Sivers asymmetry plus precise measurements for all other channels F. Bradamante

  49. future COMPASS measurements • Letter of Intent[COMPASS Collaboration] • CERN-SPSC-2009-003 SPSC-I-238, 21 January 2009: • physics case for further SIDIS data taking with the160 GeV muon beam and the transversely polarised NH3 target • further SIDIS measurement with longitudinally polarised NH3 target • Drell-Yan measurements ( O. Denisov) • DVCS measurements all presented at the CERN Worshop “New opportunities in the physics landscape at CERN”, May 11-13, 2009. • Addendum 2 to the COMPASS Proposal, June 20, 2009 • REQUEST TO CERN: • one full year of run (140 days of data taking) with transversely polarised NH3 targetwith the present muon beam and COMPASS spectrometer • one year with longitudinally polarised target • starting in 2010with the transverse part F. Bradamante

  50. projected statistical errors for the Sivers asymmetry □COMPASS 2010 h+, projection HERMES p+,DIS2007 ■ COMPASS h+, Transversity 2008 a factor of 3 with respect to the released COMPASS data future COMPASS measurements in 140 days of data taking COMPASS will perform very precise measurements of transverse spin effects over the whole x range (0.004 – 0.5) F. Bradamante

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